This invention relates to a fire extinguishing system of a type including several extinguishing units connected together, each having a heat detector for detecting an outbreak of a fire and for triggering an extinguishing process and an electric ignitor.
German patent document (DE 44 28 308 A1) discloses a fire extinguishing system having several fire extinguishing units joined together each having a device for detecting a fire and a device for triggering a fire extinguishing process. Each fire extinguishing unit of the extinguishing system disclosed in German patent document (DE 44 28 308 A1) has a heat detector and an electric ignitor for detecting the fire and for triggering the fire extinguishing process. In the fire extinguishing system disclosed in German patent document (DE 44 28 308 A1), water or foam is used as an extinguishing material. The fire extinguishing system disclosed in German patent document (DE 44 28 308 A1) is suitable only for extinguishing local fires or surface fires. The extinguishing material is conveyed to the individual extinguishing units in the fire extinguishing system disclosed in German patent document (DE 44 28 308 A1) via a network of pipes. Destruction of this network of pipes at any one point may keep many or all of the extinguishing units from being supplied with extinguishing material. Therefore, operational reliability, specifically long-term operational reliability, of the fire extinguishing system disclosed in German patent document (DE 44 28 308 A1) is poor. Furthermore, according to German patent document (DE 44 28 308 A1), power for the electric ignitor is supplied by an external source, which further detracts from the operational reliability of this fire extinguishing system.
German patent document (DE 30 21 753 C2) discloses a fire extinguishing system having a plurality of extinguishing units and one central tripping device. Each extinguishing head of the fire extinguishing system disclosed in German patent document (DE 30 21 753 C2) is connected to the central tripping device. Use of a single central tripping device severely impairs operational reliability of the fire extinguishing system disclosed in German patent document (DE 30 21 753 C2). Specifically, if the operation of the central tripping device is interrupted, the entire fire extinguishing system goes out of operation immediately because there is no system redundancy.
Russian patent document (SU-A 1 546 087) discloses an automatic fire extinguishing system with devices for detecting a fire, extinguishing devices, initiation devices, and devices for linking them together. Main disadvantages of this system are its conditional autonomy and a need for regular inspections of fire extinguishers and of starting and shut-off mechanisms, as well as a very poor extinguishing capacity of the system in comparison with fire extinguishing devices using aerosols as extinguishing measures.
British patent document (GB-A-2 028 127) discloses a fire extinguishing system having a device for generating fire extinguishing material during operation, and a device for detecting a fire and for triggering the fire extinguisher, which partly overcomes the disadvantages outlined above. However, the effectiveness of this system is inadequate, mainly because of a relatively low extinguishing potential of gaseous products of combustion, which function primarily as inert diluting agents, reducing oxygen concentrations to a level below a threshold of combustibility. The devices for detecting fires and triggering the fire extinguisher are also quite sluggish.
United States patent document (U.S. Pat. No. 3,878,897) discloses a fire extinguishing system having one or more extinguishing units connected together, each of which has a device for detecting a fire and a device for triggering an extinguishing process.
The main disadvantages of this fire extinguishing system are its poor sensitivity and functional reliability, which are further reduced during operation of the system over an extended ready stand-by period. This negative effect results from the fact that detonation cord is used as a device for detecting an outbreak of a fire, and for triggering and connecting the fire extinguishing system.
A detonation cord of any composition can be ignited only through direct contact with flames within a specific period of time. This means that the disclosed system can trigger the start of an extinguishing process only at a stage when a fire has already developed.
The likelihood that flames from a fire in its initial stages will come into contact with the detonation cord is quite small (an area to be protected is incomparably larger than a surrounding area of the detonation cord). Furthermore, the detonation cord is exposed to effects of humidity and dust, and influences of differences in air temperature related to time of day and season, which makes the detonation cord sluggish; consequently the flammability and response speed of the entire system is reduced. It is practically impossible to protect detonation cord from these negative factors, because such protection would significantly reduce sensitivity for fire detection and, ultimately, would also limit operational reliability of the system. In many cases, specifically relating to effects of corrosive and/or oil-saturated materials, local overheating, etc. may cause the cord to ignite spontaneously, and the fire extinguishing system may respond at a wrong time. Furthermore, the mechanical strength ofthe detonation cord is low, and is reduced even further over time, so that the cord may break, accidentally or on its own, becoming unusable. To keep the system in operational readiness, the detonation cords must be inspected regularly (conforming to specifications), and must be replaced as necessary.
It is an object of this invention to provide a fire extinguishing system with increased operational reliability for detecting a fire and for extinguishing the fire in its initial stages, while retaining advantageous characteristics of the system when it is in stand-by operation throughout an entire guarantee term, minimally however 10 to 15 years, and with automatic notification of a start of operation of the system to a control panel, warning-signal systems, etc.